Interest in the profile of underwater surfaces has grown significantly in the past several decades. Indeed, the ability to map and detect features in the underwater environment has become of interest in the areas of science, resource exploration, and national defense, to name a few. This has led to the development of various types of instrumentation for imaging the areas of interest.
One type of imaging system employs the use of sonar technology and translates the differences in the echo signal to locate abnormalities in a body of water. U.S. Pat. No. 5,321,667 to Audi et al represents such a system. These systems are adapted to generate information over a large scan area, but are limited in degrees of resolution, which dictates accuracy of the information, based on the ping rates and distance to the object.
A multi-platform system for acoustic surveillance is disclosed in Gaer, U.S. Pat. No. 5,231,609. In Gaer, a plurality of acoustic platforms aid in providing an accurate sonic image or shadow. Because of the use of more than one signal to produce the image, Gaer is able to track a moving object. This system, however, requires a highly sophisticated interfacing of the actual signals and signal generators to provide the sought information, thus making it a very expensive system and one that, by virtue of the amount of variables to be controlled, may be difficult to keep in synchronization.
Another system, which employs a plurality of platforms, is disclosed in Schmidt et al, U.S. Pat. No. 5,894,450. This multi-AUV system is able to obtain a profile of data by virtue of collecting the single data sets obtained by the AUVs and collating the same. This again may be a highly expensive and complicated system to use.
Another imaging system is described in Haley et al, U.S. Pat. No. 5,155,706. In Haley et al. the data obtained from different passes over the image are manipulated according to an algorithm to produce a clearer image of the desired object or feature. This system, although being lower in cost and easier to use than the multi-platform systems, admittedly produces notable false readings.
An additional patent to Haley et al, U.S. Pat. No. 5,612,928, also describes a pixel classifying system, but again this system is incapable of producing 3-D images of photo quality, but instead produces images that resemble computer renderings.
Jaffe et al, U.S. Pat. No. 4,855,961, describes another sonar imaging system employing a plurality of transmitters in conjunction with a plurality of receivers to assist in establishing a 3-D image of the object. This system, since it uses sonar for imaging, is limited in the degree of resolution available.
Another method of determining the size of an object by virtue of measurements at known spaces apart is taught by Wallin in U.S. Pat. No. 5,543,910. In Wallin, the size of an object is calculated based on a geometric model with two signals being sent from two different periscopes and at two differing angles with respect to the host devices to determine the actual distance via the geometric model from the feedback. The Wallin system is capable of location and is not a per se imaging system.
Cooper, U.S. Pat. No. 6,319,079, discloses a system with a video camera that sends back images from the underwater site. This device is also limited in that it requires a diver to operate the equipment.
Geiger, U.S. Pat. No. 5,947,051 also describes a system with a camera attached to it and discusses 3-D images. Geiger uses a system with a lidar x-y raster scanning laser beam instead of a video type of camera to obtain images. Because of the raster feature, this differs from a single fixed source. In addition, a TV camera is also disclosed as an alternate embodiment, but there is no discussion of the turbidity problems that underwater optical imaging can experience.
Patterson et al, U.S. Pat. No. 5,995,882, also describes a system with a video camera. No disclosure is made on how the images are enhanced or obtained in sufficient clarity to produce accurate representations of the object under investigation.
The use of fluorescence to detect organic materials is taught in Andrews, U.S. Pat. No. 5,929,453. In Andrews a spectrometer type of instrument is used to detect trace organics for oil spill determination but the system is not part of a moving or scanning type of device.
Finally, Schmidt et al, U.S. Pat. No. 5,687,137, describes a combination wide-scale and smaller scale measurement system which can be programmed to respond to a signal instructing it to return to an area of interest and activate finer measurements via tomography. This system, although it is sonic in design, is capable of both broad scanning and finer types of scans. No imaging specifics are addressed in this patent.